1. Field of the Invention
This invention relates to a semiconductor integrated circuit provided with an overvoltage protection circuit.
2. Description of the Related Art
In recent years, there have been developed various kinds of equipment and a charger using a rechargeable battery such as a lithium ion battery. Accordingly, there has been developed a semiconductor integrated circuit that detects voltages of a plurality of batteries connected in series and controls the voltages of the batteries based on the detected voltages.
In this kind of semiconductor integrated circuit, there is provided a protection circuit to protect internal circuits from an overvoltage due to a surge voltage applied to an input terminal, as well as a clamp circuit provided between a power supply line and a ground.
Japanese Patent Application Publication No. 2001-267496 discloses a semiconductor integrated circuit in which a plurality of input terminals shares a single protection circuit to reduce a size of the circuit. Japanese Patent Application Publication No. 2009-104455 discloses a semiconductor integrated circuit that has a clamp circuit that is provided between a power supply line and a ground and takes a reduced circuit area.
In the semiconductor integrated circuit for the battery control described above, however, there is a case in which a circuit device is connected between a neighboring pair of terminals. For example, a switching device is connected between the neighboring pair of input terminals in order to discharge electricity from the battery. When the switching device is turned on, a positive terminal and a negative terminal of the battery are short-circuited to discharge electricity, and a voltage of the battery is reduced. There is a problem with the semiconductor integrated circuit as described above that the switching device is damaged when a surge voltage is applied between the input terminals.